The overall objectives of this project is to investigate specific aspects of the overall mechanism of intestinal metabolism of cholesterol and related sterols. This includes aspects of the intraluminal and translocation phases, the cellular phase and the lipoprotein transport phases in the intestine. Studies on the intraluminal and translocation phases include determining distribution of cholesterol and sterol analogues between micellar and monomolecular phases, diffusibility through an unstirred water layer, and conditions influencing unidirectional flux of cholesterol in intestinal epithelium. Comparative studies with poorly-absorbed sterol analogues are designed to elucidate the site and mechanism of sterol discrimination. Studies on the cellular phase are largely directed toward investigations on the enzyme, cholesterol esterase with respect to conformational properties of the homogeneous enzymes, and biological studies on its role in regulating cholesterol absorption and esterification. Studies on the transport phase include the elucidation of sex differences in lymph lipoprotein transport of absorbed cholesterol, particularly with respect to synthesis and turnover of lipoprotein membrane components.